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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 9: A=$\frac{m-1}{1}$ + $\frac{m-2}{2}$ +…+ $\frac{2}{m-2}$ + $\frac{1}{m-1}$ ; B=$\frac{1}{2}$ + $\frac{1}{3}$ + $\frac{1}{4}$ +…+ $

Home/ Toán Lớp 9: A=$\frac{m-1}{1}$ + $\frac{m-2}{2}$ +…+ $\frac{2}{m-2}$ + $\frac{1}{m-1}$ ; B=$\frac{1}{2}$ + $\frac{1}{3}$ + $\frac{1}{4}$ +…+ $

Toán Lớp 9: A=$\frac{m-1}{1}$ + $\frac{m-2}{2}$ +…+ $\frac{2}{m-2}$ + $\frac{1}{m-1}$ ; B=$\frac{1}{2}$ + $\frac{1}{3}$ + $\frac{1}{4}$ +…+ $

Tháng Sáu 5, 2022 Toán học 1 Comment 0 views

Toán Lớp 9: A=$\frac{m-1}{1}$ + $\frac{m-2}{2}$ +…+ $\frac{2}{m-2}$ + $\frac{1}{m-1}$ ; B=$\frac{1}{2}$ + $\frac{1}{3}$ + $\frac{1}{4}$ +…+ $\frac{1}{n}$. Tính $\frac{A}{B}$

Comments ( 1 )

  1. lanhuongthu
    lanhuongthu
    5 Tháng Sáu, 2022 at 5:33 chiều
    Reply
    #huy
    Ta có:
    A=(n/1+n/2+…+n/(n-2)+n/(n-1))-(\underbrace{1+1+…+1}_{n-1})
    =n(1/1+1/2+1/(n-2)+1/(n-1))-(n-1)
    =n(1/2+…+1/(n-2)+1/(n-1))+1
    =n(1/2+…+1/(n-2)+1/(n-1)+1/n)
    =nB
    =>A/B=n
     

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222-9+11+12:2*14+14 = ? ( )

Lyla Anh

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